Modular endluminal stent-grafts and methods for their use

ABSTRACT

Modular endoluminal stent-grafts include at least two different sized stent-grafts which are deployed one within the other. According to one embodiment of the invention, a first stent-graft is provided having a flared end which is expandable to a first diameter and a midsection which is expandable to a second diameter smaller than the first diameter. A second stent-graft is also provided having an end which is expandable to a diameter which engages the midsection of the first stent-graft. The first embodiment of the invention is deployed by expanding the first stent-graft such that its flared end engages a large diameter vessel, then expanding the second stent-graft inside the midsection of the first stent graft and inside a small diameter vessel such that the second stent graft engages the small diameter vessel and the midsection of the first stent-graft. According to a second embodiment of the invention, the midsection of the first stent-graft is reinforced with a flexible member to restrict the midsection from ballooning. According to other aspects of the invention, the first stent-graft is provided with two flared ends and the second stent graft is provided with or without flared ends. According to still another embodiment of the invention, three or more stent-grafts of different expanded diameter are deployed one within the other.

[0001] This application is a continuation of allowed Ser. No. 08/806,739filed Feb. 27, 1997 which is a continuation-in-part of application Ser.No. 08/554,694, entitled “Self-expanding Endoluminal Stent-graft”, filedNov. 7, 1995, now U.S. Pat. No. 5,628,788, the complete disclosures ofwhich are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to an implantable prosthesis. Inparticular, the invention relates to endoluminal grafts and stent-graftswhich are deployed in a blood vessel which has a varying diameter. Theinvention is particularly suited for repairing the aortic artery anddaughter arteries, although it is not limited thereto.

[0004] 2. State of the Art

[0005] An endoluminal stent-graft typically includes tubular graftmaterial which is affixed to the inside or outside of a woven metallicstent and is delivered to the damaged site of a blood vessel via acatheter. Endoluminal stent-grafts are most often used to repair bloodvessels affected by a variety of lesions such as stenoses or aneurysms.A typical prior art stent, shown in FIGS. 1-6, is a metallic structure10 made of braided wire 12 such as stainless steel,cobalt-chromium-nickel super alloys and combinations, co-extrusions orbraised combinations of the above with tantalum, gold, platinum and thelike. Stents are also made from memory alloys such as nitinol and thelike. Typical stents are disclosed in U.S. Pat. Nos. 4,655,771 and4,954,126 to Wallsten, the complete disclosures of which are herebyincorporated herein by reference, and in U.K. Patent Number 1,205,743 toDidcott, the complete disclosure of which is also hereby incorporatedherein by reference. Generally, the wires 12 are braided with a largepick size, i.e. with relatively large interstices 14 between the wires,so that axial expansion of the stent causes a diametrical compression ofthe stent. Most often the braiding and/or the metal chosen for the wiresyields a resilient stent which is self-expanding. However, some stentsare not self-expanding and are expanded with the use of a ballooncatheter. In the case of self-expanding stents, the proximal and distalends 16, 18 of the stent are usually flared when expanded.

[0006] While endoluminal stents have been used without any graftmaterial when repairing stenoses, it is now generally preferred to use agraft material in combination with the stent when repairing stenoses aswell as when repairing aneurysms. The graft material most often used inendoluminal grafts is a PET or polytetrafluroethylene (PTFE) materialwhich is folded to reduce its size and which is attached to one or bothends of a radially expandable stent by means of sutures. When the stentself-expands or is balloon expanded, the graft unfolds around the stent.The above-referenced parent application discloses a stent-graft whichincorporates an improved self-expanding graft material.

[0007] While the primary use of endoluminal stents is to treat stenoses,stents are also sometimes used in conjunction with graft material tobridge aneurysms. The advantage of using a stent in bridging aneurysmsis that the expanded stent helps to fix the graft in place, caneliminate the need for sutures, and may provide some additionalresistance to hoop stress. Prior art FIGS. 2-5 illustrate the deploymentof a stent-graft to bridge an aneurysm.

[0008] Referring now to FIGS. 2-5, the ends of the stent 10 are axiallydisplaced inside an introducer 20 which includes an inner catheter 22having a soft (dilator) tip 24 and an outer sheath 26. The introducer 20is delivered through a blood vessel 28 with the aid of a guide wire 30which is inserted through the lumen of the inner catheter 22. Theintroducer 20 is guided over the guide wire 30 to the site of ananeurysm, in this case two adjacent aneurysms, namely distal aneurysm 32and proximal aneurysm 34. With the aid of fluoroscopy, the introducer 20is positioned so that the soft tip 24 is located distally relative tothe distal aneurysm 32. The outer sheath 26 is drawn proximally whilethe inner catheter 22 is held stationary. This releases the distal end18 of the stent 10 which self-expands to the inner diameter of thevessel 28 as shown in FIG. 3. Continued proximal movement of the outersheath 26 releases the remainder of the stent 10 as shown in FIG. 4until the proximal end 16 of the stent 10 expands to the inner diameterof the vessel 28 proximal of the proximal aneurysm 34 as shown in FIG.5, after which the introducer 20 and the guide wire 30 are removed fromthe vessel 28.

[0009] From the foregoing, it will be appreciated that by using anappropriately sized stent-graft, the aneurysms 32, 34 in FIGS. 2-5 areeffectively bridged utilizing the procedure described above. Inparticular, the stent-graft must be long enough so that its proximal anddistal ends extend beyond the aneurysms and expand into healthy areas ofthe blood vessel. Moreover, the stent-graft must be chosen to have theappropriate expanded diameter so that a good seal is made between thestent-graft and the inner wall of the blood vessel. However, thediameter should not be so large that when the stent expands, the outwardpressure of the expanding stent damages the wall of the blood vessel.

[0010] Because of the above considerations, it is difficult orimpossible to bridge an aneurysm with a stent-graft when the diameter ofthe blood vessel on either side of the aneurysm differs by anysignificant amount. For example, as shown in FIG. 6, the distal end 18of a stent-graft 10 is greatly compressed as compared to the proximalend 16 when the stent-graft is used to bridge aneurysms 32, 34 where thediameter of the vessel 28 on the proximal side 28 a of the aneurysms 32,34 is substantially greater than the diameter of the vessel on thedistal side 28 b of the aneurysms 32, 34. Depending on the nature of theparticular stent-graft, this can cause damage to the vessel on thedistal side 28 b or can result in an inward tapering of the distal end18 of the graft to a “cigar shape”. In the former situation, the damagecan result in an additional aneurysm or rupture of the vessel. In thelatter situation, the distal end 18 of the graft can obstruct the flowof blood, or jeopardize the seal between the distal end 18 and the innerwall of the vessel 28 b. In the case of obstruction, occlusion of thevessel may occur which can be catastrophic to the patient. In the caseof seal weakening, blood will enter into the aneurysmal sac and promotecontinued growth of the aneurysm.

[0011] More often than not the vessels of the vascular tree especiallyin the abdominal aortic artery exhibit the joining of vessels havingvery different diameters. For example, as shown in FIG. 7, the abdominalaortic artery 50 is the trunk from which the renal arteries, right 52,left 54 and the iliac arteries, right 56, left 58 proceed. An aorticaneurysm 60 between the renal arteries and the iliac arteries is verydifficult to bridge since the diameter of the aortic artery isapproximately 25 mm, whereas the diameter of the iliac artery is about12 mm. A stent-graft having a diameter of 27 mm will fit well in theaortic artery, but will be too large for the iliac artery. A 13 mmdiameter stent-graft will fit well in the iliac artery, but will be toosmall for the aortic artery.

[0012] The above-referenced parent application discloses a bifurcatedstent-graft which is useful in repairing an abdominal aortic aneurysmand iliac aneurysm. The bifurcated graft is located in the abdominalaortic artery just above the iliac arteries with its bifurcated endclosest to the iliac arteries. The bifurcated stent-graft effectivelybypasses an aneurysm in the aortic artery and provides a radiopaquebifurcated guide to the iliac arteries. Once the bifurcated graft isdeployed, an additional graft may be deployed in each of the iliacarteries. The additional grafts are deployed through the legs of thebifurcated stent-graft. The bifurcated legs provide separate fluidcouplings for the two additional grafts so that blood can flow from theaortic artery to both iliac arteries.

[0013] Subsequent to the development of the bifurcated stent-graft ofthe parent application, additional discoveries have been made regardingthe use of multiple stent-grafts to bridge vessels of differentdiameter. In particular, it is sometimes desirable to bridge the aorticartery with only one of the iliac arteries.

[0014] In addition, it has been discovered that in some situations wherea stent-graft has been implanted to bridge an aneurysm, the stent-graftwill continue to expand radially long after the time of implantation.This is particularly likely where there is continuous progression ofaneurysmal disease and dilation of the neck of the aneurysm. Thecontinued radial expansion of the stent-graft results in a continuedaxial shortening of the stent-graft which often results in the ends ofthe stent-graft becoming dislodged from the blood vessel whereupon theprosthesis floats free inside the aneurysm causing serious danger to thepatient.

SUMMARY OF THE INVENTION

[0015] It is therefore an object of the invention to provide endoluminalstent-grafts which are useful for bridging vessels of differentdiameter.

[0016] It is also an object of the invention to provide methods forusing endoluminal stent-grafts to bridge vessels of different diameter.

[0017] It is still another object of the invention to provide anendoluminal stent-graft with a limited radial expandability and limitedaxial compressibility.

[0018] In accord with these objects which will be discussed in detailbelow, the modular endoluminal stent-grafts of the present inventioninclude at least two different sized stent-grafts which are deployed onewithin the other. According to one embodiment of the invention, a firststent-graft is provided having a flared end which is expandable to afirst diameter and a midsection which is expandable to a second diametersmaller than the first diameter. A second stent-graft is also providedhaving an end which is expandable to a diameter which engages themidsection of the first stent-graft. The first embodiment of theinvention is deployed by expanding the first stent-graft such that itsflared end engages a large diameter vessel, then expanding the secondstent-graft inside the midsection of the first stent graft and inside asmall diameter vessel such that the second stent graft engages the smalldiameter vessel and the midsection of the first stent-graft. Both thefirst and second stent-grafts may be manufactured in a conventionalmanner using conventional materials. According to a second embodiment ofthe invention, the midsection of the first stent-graft is reinforcedwith a flexible member to restrict the midsection from ballooning due tothe outward pressure of the second stent-graft deployed within the lumenof the first stent-graft. The reinforcing member may be applied to allor a portion of the stent-graft. The reinforcing member is also usefulin preventing the stent-graft from ballooning due to the presence ofstatic blood pressure over time after implantation.

[0019] According to other aspects of the invention, the firststent-graft is provided with two flared ends and the second stent graftis provided with or without flared ends.

[0020] According to still another embodiment of the invention, three ormore stent-grafts of different expanded diameter are deployed one withinthe other.

[0021] According to another embodiment of the invention, two or morestent-grafts of different diameter are pre-coupled to each other priorto deployment and are deployed using a single introducer insubstantially one step.

[0022] According to still other aspects of the invention, the secondand/or third stent-grafts are reinforced with a flexible member torestrict the midsection from ballooning.

[0023] Additional objects and advantages of the invention will becomeapparent to those skilled in the art upon reference to the detaileddescription taken in conjunction with the provided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a side elevation view of a prior art stent;

[0025]FIG. 2 is a broken side elevation view in partial section of aprior art stent introducer during a first stage of deployment in a bloodvessel with two adjacent aneurysms;

[0026] FIGS. 3-5 are views similar to FIG. 2 showing the subsequentstages of deployment according to the prior art;

[0027]FIG. 6 is a view similar to FIG. 5 showing a blood vessel whichhas different diameters on either side of the aneurysms;

[0028]FIG. 7 is a schematic view of an abdominal aortic aneurysm;

[0029]FIG. 8 is a side elevation view of a first stent-graft in amodular system according to the invention;

[0030]FIG. 9 is a schematic view of the stent-graft of FIG. 8 deployedin an abdominal aortic aneurysm;

[0031]FIG. 10 is a view similar to FIG. 9 showing a second stent-graftin a modular system according to the invention deployed inside the firststent-graft and inside the right iliac artery;

[0032]FIG. 11 is a side elevation view of a second embodiment of a firststent-graft according to the invention having a flexible reinforcement;

[0033]FIG. 11a is a view similar to FIG. 11 of a stent-graft accordingto the invention having another type of flexible reinforcement;

[0034]FIG. 11b is a view similar to FIG. 11a of a stent-graft accordingto the invention having still another type of flexible reinforcement;

[0035]FIG. 12 is a schematic view of a modular stent-graft systemaccording to the invention having three stent-grafts where the second isdeployed inside the first and the third is deployed inside the second;

[0036]FIG. 13 is a schematic view of a modular stent-graft systemaccording to the invention in which stent-grafts of different diameterare pre-coupled to each other prior to deployment; and

[0037]FIG. 14 is a reduced schematic view of the stent-graft system ofFIG. 13 in a “pulled-down” state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Referring now to FIGS. 8-10, a first stent-graft 100 in a modularsystem according to the invention has a flared proximal end 102, aflared distal end 104, and a midsection 106. The proximal end 102 isprovided with an expanded diameter equal to or slightly larger than theinner diameter of the proximal end of an aneurysm that is to be bridged,e.g. the neck 108 of the abdominal aortic artery 50. The midsection 106is provided with an expanded diameter equal to or slightly smaller thanthe inner diameter of the distal end 55 of an aneurysm that is to bebridged, e.g. the right iliac artery 56. The stent-graft 100 may bemanufactured according to conventional methods with conventionalmaterials, but is preferably manufactured using the methods andmaterials described in the above-referenced parent application. A secondstent-graft 200 in a modular system according to the invention has aproximal end 202, a distal end 204, and a midsection 206. The expandeddiameter of the proximal end 202 is dimensioned to engage the expandedinterior of the midsection 106 of the first stent-graft 100 and theexpanded diameter of the distal end 204 is dimensioned to engage theinterior of the distal end of an aneurysm that is to be bridged, e.g.the right iliac artery 56. The stent-graft 200 may be manufacturedaccording to conventional methods with conventional materials, but ispreferably manufactured using the methods and materials described in theabove-referenced parent application.

[0039] The modular stent-grafts 100 and 200 are deployed in thefollowing manner which is illustrated by way of example in FIGS. 9 and10 which depict deployment in an abdominal aortic aneurysm. The firststent-graft 100 is compressed into an introducer (not shown) anddelivered to the a point distal of the renal arteries 52, 54 usingconventional methods (see FIGS. 2-5). The stent-graft 100 is deployedsuch that the proximal end 102 of the stent-graft 100 expands into theneck 108 of the aortic artery distal of the renal arteries 52, 54 butproximal of the aortic aneurysm 60. The expanded distal end 104 rests inthe aneurysm itself and serves to stabilize the position of themidsection 106 as shown in FIG. 9. The introducer (not shown) iswithdrawn and the second stent-graft 200 is compressed into the same oranother introducer and delivered through the first stent-graft 100 to apoint within the right iliac artery 56. The second stent-graft 200 isdeployed such that the proximal end 202 of the second stent-graftexpands into the midsection 106 of the first stent-graft 100 and thedistal end 204 of the second stent-graft expands into the right iliacartery.

[0040] As mentioned above, both the first and second stent-grafts may bemanufactured according to conventional methods with conventionalmaterials or using the methods and materials described in theabove-referenced parent application. In addition, the second stent-graftmay be made with fewer wires and/or with smaller wires in order that itfit properly in the iliac artery. The first stent-graft 100 may also beprovided with midsection reinforcement as shown in FIG. 11.

[0041] Turning now to FIG. 11, there is illustrated a stent-graft 100′which is similar to the first stent-graft 100 described above. Thestent-graft 100′ has a flared proximal end 102′, a flared distal end104′, and a midsection 106′. According to this embodiment, thestent-graft 100′ has a flexible reinforcement 105′ attached to themidsection 106′ which restricts the midsection from ballooning whenanother (second) stent-graft is expanded inside the midsection. Theflexible reinforcement 105′ may be formed from sutures, knits, weaves,braids, wires, or another stent. The reinforcement 105′ may be attachedto the inside or the outside of the midsection. Suitable materials forthe reinforcement 105′ include polyethylene terphthalate, nylon,polytetrafluoroethylene, polyolefin, polyamide, polycarbonate,polycarbonate urethane, metallic wire such as tantalum, stainless steel,titanium, annealed cobalt-chromium-nickel, etc. The reinforcement may beattached to the stent by suturing, gluing, hooks, welds or any othermethod which does not interfere with the compression of the stent. Asshown in FIG. 11, the reinforcement 105′is a substantially continuousmember or members. In addition, such a reinforcement may be applied toall or part of the second stent-graft 200 described above in order toprevent ballooning of the second stent-graft in regions of high bloodpressure, or in instances where the stent-graft is compressed axiallyduring deployment.

[0042] Turning now to FIG. 11a, there is shown a stent-graft 100″ whichis similar to the first stent-graft 100 described above. The stent-graft100″ has a flared proximal end 102″, a flared distal end 104″, and amidsection 106″. According to this embodiment, the stent-graft 100″ hasa flexible reinforcement 105″ attached to the midsection 106″ andextending along substantially its entire length. In addition, in thisembodiment, the reinforcement is formed from a series of discretemembers which are axially spaced apart from each other. An advantage ofusing discrete members is that the stent-graft can be trimmed on theoperating table without risking detachment of the ends of thereinforcement. This advantage can also be achieved with a reinforcementwhich is inlay knitted or woven into the graft component of thestent-graft, a reinforcement which is added to the outside of thestent-graft, or a reinforcement which is located between the stent andthe graft.

[0043]FIG. 11b shows a stent-graft 100′″ which is similar to the firststent-graft 100 described above. The stent-graft 100′″ has a flaredproximal end 102′″, a flared distal end 104′″, and a midsection 106′″.According to this embodiment, the stent-graft 100′″ has a first flexiblereinforcement 105′″ located between the proximal end 102′″ and themidsection 106′″ and a second flexible reinforcement 107′″ locatedbetween the distal end 104′″ and the midsection 106′″. An advantage ofthis configuration is that it allows a small amount of additional axialcompressibility which can be helpful during deployment. For example, ifthe stent is too long, it can be compressed axially to fit in thedesired space. In addition, the pitch angle of the reinforcements 105′″,107′″ can be made lower to add a small amount of longitudinalcompressibility to the stent-graft while still maintaining a restrictionon the radial expandability of the stent-graft.

[0044] Common to all of the embodiments of the reinforced stent-graft isthe feature that the reinforcement is flexible enough to allow thestent-graft to be pulled down to a small diameter for delivery to thedeployment site, but be strong enough to limit the radial expansion ofthe stent-graft beyond a diameter which is substantially equal to theresting diameter of the stent-graft.

[0045] The modular stent-graft system of the invention may include morethan two stent-grafts. For example, as shown in FIG. 12, a modularsystem may include three stent-grafts 300, 400, 500 for bridging twoaneurysms 604, 608 in a blood vessel 600 which exhibits three differentdiameters 602, 606, 610. As shown in FIG. 12, the first stent-graft 300has a flared proximal end 302, a non-flared distal end 304, and amidsection 306. The second stent-graft 400 has a non-flared proximal end402, a non-flared distal end 404, and a midsection 406. The thirdstent-graft 500 has a flared proximal end 502, a non-flared distal end504, and a midsection 506. The flared proximal end 302 of the firststent-graft 300 has an expanded diameter which fits securely in thelarge diameter portion 602 of the blood vessel 600 proximal of the firstaneurysm 604. The second stent-graft 400 has a substantially constantexpanded diameter which causes its proximal end 402 to fit securely inthe midsection 306 of the first stent-graft 300 and its midsection 406to fit securely in the smaller diameter section 606 of the blood vessel600 between the first aneurysm 604 and the second aneurysm 608. Theflared proximal end 502 of the third stent-graft 500 has an expandeddiameter which fits securely in the midsection 406 of the secondstent-graft 400; and the non-flared distal end 504 has an expandeddiameter which fits securely in the smallest diameter portion 610 of theblood vessel 600 distal of the second aneurysm 608. The modularstent-grafts of FIG. 12 are deployed in a manner similar to thestent-grafts shown in FIG. 10, i.e. by deploying the proximalstent-graft first, and then following with distal stent-grafts. AlthoughFIG. 12 shows three stent-grafts with increasingly smaller diameters,the proximal to distal diameter change need not be from larger tosmaller. For example, if the aneurysm 608 were located proximal of theaneurysm 604, the stent-grafts could be deployed in a different order orin the same order but with their proximal and distal ends reversed. Thatis, the stent-graft 400 could be deployed first and the stent-grafts 300and 500 could be deployed inside the stent-graft 400. In this situation,it would be advantageous for the entire length of the stent-graft 400 tobe reinforced. Alternatively, the stent-graft 300 could be deployedfirst with its end 302 being deployed distally, etc.

[0046] Referring now to FIGS. 13 and 14, a modular stent-graft system700 is shown. The stent-graft system 700 has three stent-grafts 300′,400′, and 500′ which are similar to the stent-grafts 300, 400, and 500described above. As shown in FIG. 13, the primed reference numerals(e.g. 302′) refer to features of the stent-grafts 300′, 400′, and 500′which are similar to features of the stent-grafts 300, 400, and 500described above. According to this embodiment of the invention, theproximal end 402′ of the stent-graft 400′ is pre-coupled to themidsection 306′ of the stent-graft 300′ and the proximal end 502′ of thestent-graft 500′ is pre-coupled to the midsection 406′ of thestent-graft 400′. The pre-coupling may be effected at the time ofmanufacture, or by a practitioner prior to deployment of the modularstent-graft system. As shown in FIG. 13, the pre-coupling isaccomplished with sutures 401′ and 501′. However, the stent-grafts mayalso be coupled to each other by wires, adhesives, welds, or by usingany other suitable coupling method. After the stent-grafts 300′, 400′,and 500′ are coupled to each other, they are “pulled down” as a singleunit with the aid of an introducer to a compressed state as shown inFIG. 14 for deployment.

[0047] There have been described and illustrated herein severalembodiments of modular endoluminal stent-grafts and methods for theiruse. While particular embodiments of the invention have been described,it is not intended that the invention be limited thereto, as it isintended that the invention be as broad in scope as the art will allowand that the specification be read likewise. Thus, while particulardimensions and materials have been disclosed, it will be appreciatedthat other dimensions and materials could be utilized. Also, while thestent-grafts have been shown for use in bridging aneurysms, it will berecognized that the modular system of stent-grafts could be used tobridge other types of lesions. Moreover, while particular configurationshave been disclosed in reference to flared ends and reinforcing members,it will be appreciated that other configurations could be used as well.For example, the modular stent-graft 100 described with reference toFIG. 10 could be provided with a single flared end, the proximal end,rather than two flared ends, in order to fit in certain tortuousarteries. Also, it is possible to utilize a bifurcated stent (as shownin the parent application) as a component in a modular stent system anduse an occluding device to block one of its legs.

[0048] It will therefore be appreciated by those skilled in the art thatyet other modifications could be made to the provided invention withoutdeviating from its spirit and scope as so claimed.

1. A modular endoluminal stent-graft system for bridging a lesion in ablood vessel having a first large diameter on one side of the lesion anda second small diameter on the other side of the lesion, said systemcomprising: a) a first stent-graft having a first end, a second end, anda midsection, said first end of said first stent-graft having anexpanded diameter equal to or slightly larger than the first largediameter of the blood vessel, said midsection of said first stent-grafthaving an expanded diameter which is smaller than said expanded diameterof said first end of said first stent-graft; b) a second stent-grafthaving a first end, a second end, and a midsection, said first end ofsaid second stent-graft having an expanded diameter equal to or slightlylarger than said expanded diameter of said midsection of said firststent-graft and said second end of said second stent-graft having anexpanded diameter which is equal to or slightly larger than the secondsmall diameter of the blood vessel, such that in a deployed orientation,said first end of said first stent-graft is adapted to engage the firstlarge diameter of the blood vessel, said first end of said secondstent-graft securely engages said midsection of said first stent-graftto hold said second stent graft substantially fixed relative to saidfirst stent-graft, and said second end of said second stent-graftengages the second small diameter of the blood vessel.
 2. A systemaccording to claim 1, wherein: said first end of said first stent-graftis flared.
 3. A system according to claim 2, wherein: said second end ofsaid first stent-graft is flared.
 4. A system according to claim 1,wherein: said first end of said second stent-graft is flared.
 5. Asystem according to claim 4, wherein: said second end of said secondstent-graft is flared.
 6. A system according to claim 1, wherein: atleast said midsection of said first stent-graft is reinforced with aflexible material.
 7. A system according to claim 6, wherein: saidflexible material is selected from the group consisting of polyethyleneterphthalate, nylon, polytetrafluoroethylene, polyolefin, polyamide,polycarbonate, polycarbonate urethane, and metallic wire.
 8. A systemaccording to claim 6, wherein: said flexible material is selected fromthe group consisting of sutures, knits, weaves, braids, wires, andstents.
 9. A modular stent-graft system, comprising: a) a firststent-graft having a first end, a second end, and a midsection, saidfirst end of said first stent-graft having an expanded first diameterand said midsection of said first stent-graft having an expanded seconddiameter which is smaller than said expanded first diameter; b) a secondstent-graft having a first end, a second end, and a midsection, saidfirst end of said second stent-graft having an expanded third diameterequal to or slightly larger than said expanded second diameter of saidmidsection of said first stent-graft, said second end of said secondstent-graft having an expanded fourth diameter equal to or smaller thansaid third diameter, such that in a deployed orientation, said first endof said second stent-graft securely engages said midsection of saidfirst stent-graft to hold the second stent-graft substantially fixedrelative to said first stent-graft.
 10. A system according to claim 9,wherein: said first end of said first stent-graft is flared.
 11. Asystem according to claim 10, wherein: said second end of said firststent-graft is flared.
 12. A system according to claim 9, wherein: saidmidsection of said first stent-graft is reinforced with a flexiblematerial.
 13. A system according to claim 12, wherein: said flexiblematerial is selected from the group consisting of polyethyleneterphthalate, nylon, polytetrafluoroethylene, polyolefin, polyamide,polycarbonate, polycarbonate urethane, and metallic wire.
 14. A systemaccording to claim 12, wherein: said flexible material is selected fromthe group consisting of sutures, knits, weaves, braids, wires, andstents.
 15. A system according to claim 9, further comprising: c) athird stent-graft having a first end, a second end, and a midsection,said first end of said third stent-graft having an expanded fifthdiameter, wherein said midsection of said second stent-graft has anexpanded sixth diameter equal to or slightly smaller than said expandedfifth diameter of said first end of said third stent-graft, such that ina deployed orientation, said first end of said third stent-graft engagessaid midsection of said second stent-graft.
 16. A system according toclaim 15, wherein: said first end of said third stent-graft is flared.17. A system according to claim 1, wherein: said first end of saidsecond stent-graft is coupled to said first stent-graft by one ofsutures, wires, adhesive and welds.
 18. A system according to claim 1,wherein: said first end of said second stent-graft is coupled to saidmidsection of said first stent-graft.
 19. A method of bridging a lesionin a blood vessel having a first large diameter on one side of thelesion and a second small diameter on the other side of the lesion, saidmethod comprising: a) obtaining a first stent-graft having a first end,a second end, and a midsection, said first end of said first stent-grafthaving an expanded diameter equal to or slightly larger than the firstlarge diameter of the blood vessel, said midsection of said firststent-graft having an expanded diameter which is smaller than saidexpanded diameter of said first end of said first stent-graft; b)obtaining a second stent-graft having a first end, a second end, and amidsection, said first end of said second stent-graft having an expandeddiameter equal to or slightly larger than said expanded diameter of saidmidsection of said first stent-graft and said second end of said secondstent-graft having an expanded diameter which is equal to or slightlylarger than the second small diameter of the blood vessel; c) deployingsaid first stent-graft by expanding said first stent-graft such thatsaid first end of said first stent-graft engages the first largediameter of the blood vessel; and d) deploying said second stent-graftby expanding said second stent-graft such that said first end of saidsecond stent-graft engages said midsection of said first stent-graftsuch that said second stent-graft is substantially fixed relative tosaid first stent-graft and said second end of said second stent-graftengages the second small diameter of the blood vessel.
 20. A methodaccording to claim 19, further comprising: e) obtaining a thirdstent-graft having a first end, a second end, and a midsection; and d)deploying said third stent-graft by expanding said third stent-graftsuch that said first end of said third stent-graft engages saidmidsection of said second stent-graft.
 21. A modular endoluminalstent-graft system for bridging a lesion in a blood vessel having afirst large diameter on one side of the lesion and a second smalldiameter on the other side of the lesion, said system comprising: a) afirst stent-graft having a first end, a second end, and a midsection,said first end of said first stent-graft having an expanded diameterequal to or slightly larger than the first large diameter of the bloodvessel, said midsection of said first stent-graft having an expandeddiameter which is smaller than said expanded diameter of said first endof said first stent-graft; b) a second stent-graft having a first end, asecond end, and a midsection, said first end of said second stent-grafthaving an expanded diameter equal to or slightly larger than saidexpanded diameter of said midsection of said first stent-graft and saidsecond end of said second stent-graft having an expanded diameter whichis equal to or slightly larger than the second small diameter of theblood vessel, such that in a deployed orientation, said first end ofsaid first stent-graft is adapted to engage the first large diameter ofthe blood vessel, said first end of said second stent-graft engages saidmidsection of said first stent-graft, and said second end of said secondstent-graft is adapted to engage the second small diameter of the bloodvessel wherein at least said midsection of said first stent-graft isreinforced with a flexible material.
 22. A modular stent-graft system,comprising: a) a first stent-graft having a first end, a second end, anda midsection, said first end of said first stent-graft having anexpanded first diameter and said midsection of said first stent-grafthaving an expanded second diameter which is smaller than said expandedfirst diameter; b) a second stent-graft having a first end, a secondend, and a midsection, said first end of said second stent-graft havingan expanded third diameter equal to or slightly larger than saidexpanded second diameter of said midsection of said first stent-graft,said second end of said second stent-graft having an expanded fourthdiameter equal to or smaller than said third diameter, such that in adeployed orientation, said first end of said second stent-graft engagessaid midsection of said first stent-graft wherein at least saidmidsection of said first stent-graft is reinforced with a flexiblematerial.
 23. A method of bridging a lesion in a blood vessel having afirst large diameter on one side of the lesion and a second smalldiameter on the other side of the lesion, said method comprising: a)obtaining a first stent-graft having a first end, a second end, and amidsection, said first end of said first stent-graft having an expandeddiameter equal to or slightly larger than the first large diameter ofthe blood vessel, said midsection of said first stent-graft having anexpanded diameter which is smaller than said expanded diameter of saidfirst end of said first stent-graft wherein at least said midsection ofsaid first stent-graft is reinforced with a flexible material; b)obtaining a second stent-graft having a first end, a second end, and amidsection, said first end of said second stent-graft having an expandeddiameter equal to or slightly larger than said expanded diameter of saidmidsection of said first stent-graft and said second end of said secondstent-graft having an expanded diameter which is equal to or slightlylarger than the second small diameter of the blood vessel; c) deployingsaid first stent-graft by expanding said first stent-graft such thatsaid first end of said first stent-graft engages the first largediameter of the blood vessel; and d) deploying said second stent-graftby expanding said second stent-graft such that said first end of saidsecond stent-graft engages said midsection of said first stent-graft andsaid second end of said second stent-graft engages the second smalldiameter of the blood vessel.